El#concepto#darwiniano#de#la#allostasis…##
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ABSTRACT#
The#Darwinian#concept#of#allostasis.#Epigenetic#programming#
!At!the!end!of!last!Century!the!concept!of!allostasis!was!proposed!as!the!group!of!
responses! from! live! beings,! regulated! by! the! brain,! leading! to! maintain! the!
organism!balance!and,!therefore,!to!survival.!!But!this!concept!has!clear!Darwinian!
significance.!!!
Questions) established) in) the) XX) Century.)
The! HPA! (hypothalamusDpituitaryD
adrenal!gland)!axis!is!the!most!important!among!all!regulatory!systems!triggered!
by! allostasis,! and! it! is! programmed! during! the! gestational! period! in! mammals.!
Under!a!stressful!situation!the!mother!HPA!axis!operates!secreting!high!amounts!
of! glucocorticoids! (GC)! that! get! into! the! foetus! affecting! to! the! normal! HPA!
programming;! this! abnormal! development! is! irreversible! in! adulthood! and! will!
also!reduce!birth!weight.!Besides,!it!is!a!risk!factor!for!possible!adult!pathologies!
such!as!diabetes!mellitus!type!2,!cardiovascular!disease!or!chronic!hypertension.
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The!reason!is!the!decrease!of!glucocorticoid!receptors!(GR)!in!hippocampus,!since!
they! are! crucial! for! the! negative! feedback! of!HPA! axis.!However,! the!mechanism!
by! which! GC! reduce! GR! expression! in! hippocampus! was! unknown! in! the! XX!
Century.
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Questions) established) in) the) XXI) Century.)
A! number! of! research! articles!
published! in! the! XXI! Century! reporting! information! about! the! epigenetic!
mechanism! involved! in! the! hippocampal! reduction! of! GR! are! selected! and!
presented.! The! main! epigenetic! mechanisms! known! up! to! date! are! also!
mentioned.
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Finally,! the! great! therapeutic! possibilities! of! the! epigenetic! mechanisms! in! the!
near! future! are! enunciated! as! well! as! the! possible! explanation! of! evolutional!
processes.!!
Keywords:)
Allostasis;! gestational! period;! HPA! axis;! epigenetic! programming;!
Darwin.!
1.#INTRODUCCIÓN#
El! concepto! de! allostasis,! establecido! a! finales! del! siglo! XX,! recoge! el!
conjunto! de! sistemas! que! se! activan! en! los! organismos! vivos,! regidos! por! el!
cerebro,! para! conservar! el! equilibrio! interno! y,! por! tanto,! la! supervivencia.! Todo!
ello!cuando!factores!externos!al!organismo,!o!internos!a!él,!alteran!su!homeostasis!
provocando! un! estado! de! emergencia.! Los! factores! internos! que! producen! el!
desequilibrio!pueden!ser!un!aumento!de!pH,!de!temperatura,!una!infección,!etc.,!y!
los!externos!pueden!ser!una!alteración!climática,!falta!de!comida,!o!un!depredador!
que! nos! ataca.! Y! todas! las! respuestas! que! los! organismos! habilitan,! con! fines! de!
